144 MANURE. 



208. Each substance used for a manure, cannot 

 be considered in detail. Their general composition 

 only, will be mentioned. Among the mixed manures, 

 poudrette, and guano, rank next to night soil. Pou- 

 drette, is night soil partly dried in pans and mixed 

 up with variable quantities of ground peat and plas- 

 ter. Its value will depend on the circumstance, 

 whether its ammonia is saved, or lost, in the manu- 

 facture. If sulphate or muriate of lime is added be- 

 fore drying, then the volatile carbonate of ammonia, 

 will be changed into sulphate of ammonia, and sal 

 ammoniac. Thus not only the most valuable portion 

 of night soil will be retained, but, the salts of lime 

 will be much increased. The peat not only retains 

 a portion of gaseous ammonia, but its geine by this 

 act is rendered more soluble. All night soil from 

 vaults has began to evolve ammonia, hence the ad- 

 vantage of mixing ground peat or plaster with night 

 soil, before drying. 



209. It is evident therefore, that the value of pou- 

 drette, depends on the skill, and honesty of the man- 

 ufacturer. But allowing these to be what they 

 should be, no consumer of poudrette will think him- 

 self wronged, if he discovers ground peat in the arti- 

 cle; and allowing this, and the plaster, or other salts 

 added, to compose one-half the weight of this ma- 



